Preloaded pivot mount for variable pitch propeller blades



sept. 4, 1951 PITCH PROPELLER BLADES 3 Sheets-Sheet 1 Filed NOV. 24, 1948 Raw/04a? IVW/FEV ATTOR N EYS SePt- 4, 1951 P. F. HAcKx-:THAL ET AL 2,566,884

' PRELOAOEO PIVOT MOUNT FOR VARIABLE PITCH PROPELLER BLADES 3 Sheets-Shea?l 2 Filed Nov. 24, 1948 T l F2401. F Hanns-MWL Ram una@ Knee-r Sept. 4, 1951 P. F. HACKETHAL ET Al.

PRELOADED PIVOT MOUNT FOR VARIABLE FITCH PROPELLER BLADES 3 Sheets-Sheet 3 Filed NOV. 24, 1948 ATTORNEYJ l Patented Sept. 4, 1951 PRELOADED PIVOT MOUNT lFOR VARIABLE PITCH PROPELLER BLADES Paul F. Hackethal, Wentworth, N. H., and Romuald Karey, Cockeysville, Md., assignors to Everel Propeller Corporation, Baltimore, Md., a

corporation of Maryland Original application May 7, 1945, Serial No.

592,496. Divided and this application November 24, 1948, Serial No. 61,794

6 Claims. l

This invention relates to propellers for aircraft, and is a division of our copending application Serial No. 592,496, :tiled May 7, 1945 (now abandoned), which is a continuation-impart of that described in our copending application Serial No. 508,352. led October 30, 1943; which matured into Patent No. 2,528,236 on October 31, 1950.

More particularly the present invention relates to improved means for rotatably mounting the propeller blades in a hub for pitch changing movement therein with particular reference to axially expansible means interposing between the transverse shaft coupling tube of the hub and a rotary flanged sleeve which pivotally mounts the blade in the hub to preload the antifriction bearings for the sleeve. The invention is additionally directed to sealing means to inhibit leakage of lubricant from the hub.

An automatic pitch changing propeller has been developed in which the shanks of the blades are secured in llanged sleeves, these in turn being mounted for rotation in the hub. The construction of the blade sleeves is such that the longitudinal axes of the blades are at an angle to the rotational axes of the sleeves with the result that, in night, the rotational position of the blades with respect to the hub, and as a consequence, the pitch angle of the blades is affected by various conditions encountered in iiight, principally the relationshipof the following forces reacting on the blades: aerodynamic force due to thrust reacting on the blades in a direction normal to the plane of rotation of the propeller, which tends to rotate the angularly disposed blades about the arc of a cone in a forwardly y ment and in correctly and accurately preloading the blade bearings.

An important object of the invention is to providel an improved means for preloading the blade bearings in automatic variable pitch propellers.

Another object of the invention is to provide (Cl. 16o-23) approved means for preloading the blade bearings in an automatic variable` pitch propeller which are easily and accurately adjustable to within fine limits to a predetermined. load after assembly of the hub, and incorporating means for positively locking the preloading means in adjusted position.

A still further object is to provide means for accurately and easily adjusting propellers of the above character for desired limits of pitch change movement of the blades.

Yet another object of the invention is the provision of an improved oil seal for such propellers and an improved means for installing the same.

With these and other important objects in view which may be incident to our improvements, the invention consists in the parts and combinations to -be hereinafter more fully set forth and claimed, with the understanding that various changes may be made therein by those skilled in the art without departing from -the spirit of the invention or exceeding the scope ol the appended claims.

Inorder to make the invention more clearly understood, reference is made to the accompanying drawings which are employed to illustrate means for carrying the invention into practical effect without limiting the same to the particular constructions shown by way of illustration:

In the drawings:

Figure 1 is a transverse sectional view of a propeller hub according to the'invention;

Figure 2 is a cross sectional view taken substantally along the lines 2-2 of Figure l looking in the direction of the arrows;

Figure 3 is a cross sectional view taken substantially along the line 3--3 of Figure 1 looking in the direction of the arrows;

Figure 4 is a transverse sectional view of a modified form of hub construction according to the invention, and ,y

Figure 5 is an enlarged fragmental view in cross section of the oil seal shown in Figure 4.

While the improvements constituting this invention are shown and described as applied to a two blade, automatic variable pitch propeller, the invention is not to be construed as being so limited as it is obvious that the improvements are equally applicable to propellers having a single or more blades and thatfcertain of the improvements, particularly with reference to blade and propeller balancing, are applicable to other types of detachable blade propellers and rotors.

Referring now to the drawings, the two blade propeller hub, as will be best seen in Figures 2A and 3, comprises a cylindrical barrel portion I and a transverse shaft coupling element 2. The shaft coupling element 2 may be either integrally formed with the barrel portion I, or, preferably, machined as a separate sleeve and inserted transversely through the barrel I and secured to opposite walls thereof by suitable means such as welding. as illustrated in Figure 2. The shaft coupling element 2 is integrally machined to provide a splined bore 3 to t a correspondingly splined end of a propeller shaft 4.

Opposite ends of the shaft bore 3 are taper bored to provide a front cone seat 5 and a rear cone seat 6 adapted to seat respectively the usual front and rear hub centering cones I and 3 which are drawn toward each other. to center and secure the hub on the propeller shaft, by a hollow nut 9 screw threaded on the end of the propeller shaft 4. It is to be noted that the nut 9 is provided at its inner end with an external flange I9 Awhich cooperates with an internal groove Il in the front cone 1 to force the front cone toward the rear cone when the nut is drawn up, and to pull the front cone forwardly when the nut 9 is backedV off. As an additional means to prevent accidental longitudinal displacement of the front cone 1 a snap ring I2 is provided in the forward end of the bore of the blade coupling element. Formed on, or secured to. opposite sides of the blade coupling element 2 is a cylindrical boss I3 axially aligned with the longitudinal axis of the blade barrel i. Each of these bosses is provided with a cylindrical screw threaded socket I4.

As seen in Figure i, the blade barrel i has a longitudinal bore at each end to provide blade receiving sockets I5 for mounting opposed propeller blades, not shown. Each of these sockets is somewhat enlarged, as indicated at i1, to receive a thrust bearing structure to be described `later, and is provided with an internal groove I8 adjacent the end of the barrel.

Positioned in each end of the barrel 2 is a blade mounting sleeve I 9 centrally bored adjacent its inner end to provide an internally flanged bearing socket 20. Also adjacent the inner end of each sleeve I9 is an external peripheral flange 2I.

Positioned about each of the sleeves I9 is an annular thrust bearing element designated generally as 22 and consisting of parallel ball races 23 and 24 between which are positioned bearing balls 25. The inner ball race 23 engages the outer surface of the sleeve I9 and is seated against the external flange 2|, while the outer race 24, which is free to rotate relative to the sleeve, engages the inner surface of the enlarged bore I1 of the blade barrel. Outward movement of the thrust bearing 22 is blocked by means of a snap ring 26 fitted into the groove I3. An oil seal, designated generally as 21 and which will be described in more detail later, is held within a retaining ring 29 positioned between the outer ball race 24 and snap ring 2'6 while an additional sealing ring 30 is provided between the ball race 24, the ring member 29, and the inner surface of the barrel I. Sealing elements 21 and 30 effectively prohibit leakage of oil from the interior of the hub past the relatively movable parts.

In addition to the thrust' bearing 22, a second journal is provided for additionally supporting the sleeve I9 within the hub barrel. This latter journal comprises a radial ball bearing 3l, the

outer race of which is seated within the internally hanged socket 20 of the-blade sleeve, and the inner racer.V carried by the cylindrical boss I3.

In order tog' load the bearings 22 and 3| to secure optimum operation thereof, a preloading device is incorporated in the hub structure. One embodiment of preloading device is shown in Figure 3 and consists of a pair of resilient cup shaped annular discs 32 and 33 which are positioned on the boss I3 between thebearing 3| and the shaft coupling sleeve 2. The discs 32 and 33 have their concave surfaces facing each other and their outer peripheral edges in engagement, the inner periphery of the outer disc 33 engaging the bearing 3| and the inner periphery of the inner disc 32 lying adjacent the shaft coupling sleeve 2. There is preferably positionedbetween the inner peripheries of the two discs a spacing ring 34 which serves to limit the amount of permissible compression; and there may be inserted between the disc 32 and the shaft coupling sleeve 2 a washer 35 of suitable thickness toinsure the desired load upon the bearings. The washer 35 may be formed of laminated shim material whereby the desired thickness of the washer for any given assembly may be readily varied. In assembling the hub, the discs 32 and 33 together with the associated washer and spacing ring are placed on the boss I3 and the blade sleeve with its bearings 22 and 3| is inserted in the Ysocket VI5 of the hub. A suitable assembly tool, provided with a flange to engage the inner end of the blade sleeve, is screwed into the threaded socket of boss I3 to draw the blade sleeve inwardly and compress the discs 32 and 33. The snap ring 26 is then placed in groove I3 and the tool removed. The load by the discs 32 and 33 maintains the sleeve in assembled position.

Each of the sleeves I9 is provided with a, bore 36 extending from the outer end thereof to adjacent the inner end l'at a predetermined and calculated angle to the axis of rotation of the sleeve in the hub. The angular bore 36 is for the reception of the shank of a propeller blade which is held against axial displacement therein by screw threaded engagement with internal threads 31 formed adjacent the inner end of the bore.

To prevent leakage of oil from the interior of the hub through the blade sleeves, the inner end of the sleeve bore is fitted with a closure disc 49, held therein by a snap ring 50 and sealed into oil-tightl engagement with the sleeve by a gasket 5 I It is advantageous in automatic pitch change propellers that the pitch changing rotation of the blades be synchronized and to this end, each of the blade sleeves I9 is provided on its inner end with a bevel gear segment 63. These gear segments are operatively connected by a. pinionlike member 64 pivotally mounted on a flanged stud member -65 which is inserted through an aperture in the wall of the blade barrel I and secured thereto by cap screws I6 passing through the stud flange and into the blade barrel. Preferably shim material 61 is interposed between the stud flange and the blade barrel to adjust position of the pinion 65 radially in the blade barrel, that is, toward the axis of rotation of the blade sleeves to eliminate back lash between the pinion and the mating gear segments 63.

To limit the rotational movement of the sleeves I9 and, as a consequence, to regulate the magnitude and the degree of pitch increasing and/or pitch decreasing movement of the blades, each sleeve is provided with a segmental abutment v68 from outside the hub barrel.

member 88 on its inner end, diametrically opposite the gear segment 63. Each of these abutment members 68 moves 'in the path of a pair of stop screws 69 and 10 carried by the hub barrel 2 and adjustable toward and away from the abutment Preferably the stop screws 69 and 10 are threaded through sleeves 1| which are of suftlcient size and weight, together with the screws `69 and 10, to substantially counterbalance the pinion 64 and its supporting stud on the opposite side of the hub. Also there is preferably positioned between the heads of the screws 69 and 18 and the sleeves 1l Washers 12 composed of laminated shim material for accurately adjusting the screws and maintaining their adjusted positions. Preferably the sleeves 1i are rigidly secured to the hub 'barrel as by brazing or welding, but alternately they may be screw threaded into the barrel for further adjustment of the stops.

Lubricant within the propeller hub is subjected to rather high centrifugal force in the operating propeller which tends to force it out past the blade sleeve. One type of oil sealing element which we have found very efficient in preventing leakage is a chevron type shown in the enlarged view, Figure 5. This is a ring 13 of neoprene or other suitable oil resistant material shaped in cross section substantially in the form of a V defining laterally extending wings 14 with a rib 14a in the angle of the V. Usually two or more of these rings are used in a seal and maintained under axial pressure, the rib serving, when under pressure, to expand the wings 14 laterally into close engagement with its cooperating surfaces of the hub structure, in this case the side wall of the retaining ring 29 and the outer periphery of the blade sleeve. Considerable difficulty has been encountered heretofore, however, when comprssing,r a number of these rings, in maintaining them in axial alignment due to the tendency of the rib to overlap the angular face of the adjacent ring. To eliminate this defect, we interpose a thin annular disc 15 between adjacent rings to provide a substantial, flat surface normal to the direction of compression movement of the rib. In Figure 3, the disc 15 is omitted, but this is usually inadvisable.

A modified form of bearing preloading device which has been found highly effective in equally loading the blade bearings because of its high degree of close and accurate adjustment is illustrated in Figure 4. This preloading device consists of an internally screw threaded sleeve 1B, and an externally screw threaded tubular element 11 threadedly engaging the sleeve li for telescoping movement with respect thereto. The sleeve 15 is rigidly secured to a short stud |3A, formed on the side of the shaft coupling sleeve 2 coaxially with the barrel I. A ring 19 surrounds the sleeve 16 and is provided with an internal flange 1B which is seated upon the outer end of tubular element Tl. The opposite end of the ring 19 has an external flange 80 which forms a seat for the inner race of the bearing 3|.

The outer end of tubular element 11 is provided with slots (not shown) for engagement by a suitable tool to screw it into sleeve 16. The position of element 411 within sleeve 16 determines the `position of ring 19 and consequently the degree of preloading. In order to maintain the adjustment of element 11 within the sleeve 'IG against accidental displacement, the element 11 is slit longitudinally, as indicated at 8|, and provided with a tapered axial the blade sleeves.

6 bore 82 in which is screw threaded a taper screw 88.

4in assembling the hub shown in Figure 4, all bearing preload parts are moved inwardly by screwing the elements 11 into the sleeves 18. The blade sleeves I9 with their bearings and oil seals in place are inserted into the hub sockets. the inner race of the bearing 3l about the ring 18 and in engagement with the external flange 80. The blocking snap rings 26 are then inserted in their grooves I8 and the elements 11 backed out with respect to the sleeves 18 until the bearings are loaded as desired which may be ascertained by suitable torque measuring instruments. The tapered plugs 83 are then screwed up into the sockets 82 which spread the threaded elements 11 into tight frictional engagement with the sleeves 16.

The above operations are of course performed before the insertion of the closure discs 48 into These may now be inserted, first inserting the sealing gasket 5|, then the disc 49, and finally the snap ring 50.

From the foregoing it will be seen that we have provided a propeller which incorporates various improvements in structure which leads to the efficiency of the unit and, while only the preferred structure is set forth, it will be appreciated that equivalents for the structural elements may be substituted for those disclosed without departing from the spirit and scope of the following claims.

We claim:

l. In a propeller construction, a hub having a tubular shaft coupling element extending transverselv therethrough and a blade mounting socket extending radially outward from said element, a blade receiving sleeve rotatably mounted in the socket, a peripheral flange on the inner end of the sleeve, anti-friction bearing means on the sleeve and engaging the iiange, means in the socket and engaging the bearing means to block outward displacement of the sleeve from said socket, and loading means interposed between the shaft coupling element and sleeve for pressing the latter outward in said socket to preload sai-i bearing, said loading means including a first part engaging the shaft coupling element, a second part engaging the first part and including an anti-friction bearing engaging said sleeve, a'nd means for adjusting one part relative to the other part to thereby adjust the pressure exerted by the loaded means.

2. In -a propeller construction, a hub having a tubular shaft coupling element extending transversely therethrough and a blade mounting socket extending radially outward from said element, a blade receiving sleeve rotatably mounted in the socket, a peripheral flange on the inner end of the sleeve, anti-friction bearing means on the sleeve and engaging the flange, means in the socket and engaging the bearing means to block outward displacement of the sleeve from said socket, and loading means interposed between the shaft coupling element and sleeve for pressing the latter outward in said socket to preload said bearing, said loading means including a pair of resilient cupped disc members having their concave sides facing each other with their peripheral edges in engagement, the convex face of one disc engaging the shaft coupling element. an antifriction bearing engaging the inner end of said sleeve, and the second cupped disc having its convex face engaging the last named anti-friction bearing.

3. In a. propeller construction, a hub having a tubular shaft coupling element extending transversely therethrough and a blade mounting socket extending radially outward from said element, Ya blade receiving sleeve rotatably mounted in the socket, a peripheral flange on the inner end of the. sleeve, anti-friction bearing means on the sleeve and engaging the ange, means in the socket and engaging the bearing means to block outward displacement of the sleeve from. said socket, and loading means interposed between the shaft coupling element and sleeve for pressing the latter outward in said socket to preload said bearing, said loading means including a pair of resilient cupped disc members having their concave sides facing each other with their peripheral edges in engagement, the convex face of one disc engaging the shaft coupling element, an anti-friction bearing engaging the inner end of said sleeve, the second cupped disc having its convex face engaging the last named anti.- triction bearing, and shim means interposed beof the sleeve, anti-friction bearing means on the sleeve and engaging the flange,V means in the socket and engaging the bearing means to block tween said ilrst named disc and the shaft coupling element for adjusting the pressure exerted by said resilient discs.

4.' In a propeller construction, a hub having a tubular shaft coupling element extending transversely therethrough and a blade mounting socket extending radially outward from said element, a blade receiving sleeve rotatably mounted in the socket, a. peripheral flange on the inner end of the sleeve, anti-friction bearing means on the sleeve and engaging the flange, means in the socket and engaging the bearing means to block outward displacement of the sleeve from said socket, and loading means interposed between the shaft coupling element and sleeve for pressing the latter outward in said socket to preload said bearing, said loading means including a pair of resilient cupped disc members having their concave sides facing each other with their peripheral edges in engagement, the convex face of one disc engaging the shaft coupling element, an anti-friction bearing engaging the inner end of said sleeve, the second cupped disc having its convex face engaging the last named anti-friction bearing, shim means interposed between said first named disc and the shaft coupling element for adjusting the pressure exerted by said resilient discs, and spacer means interposed between said discs.

5. In a propeller construction, a hub having a tubular shaft coupling element extending transversely therethrough and a. blade mounting socket extending radially outward from said element, a blade receiving sleeve rotatably mounted in the socket, a peripheral flange on the inner end outward displacement of the sleeve from said socket, and loading means interposed between the shaft coupling element and sleeve for pressing the latter outward in said socket to preload said bearing, said loading means including an antifriction bearing engaging the inner end of said sleeve, a tubular member engaging said bearing. a second member engaging the shaft coupling element and in engagement with the iirst member for longitudinal adjustment with respect thereto. and means for fixing the adjusted position of said members.

' 6. In a propeller construction, a hub having a tubular shaft couplingelement extending transversely therethrough and a blade mounting socket extending radially outward from said element, a blade receiving sleeve rotatably mounted in the socket, a peripheral flange on the inner end of the sleeve, anti-friction bearing means on the sleeve and engaging the ange, means in the socket and engaging the bearing means to block outward displacement of the sleeve from said socket, and loading means interposed between the shaft coupling element and sleeve for pressing the latter outward in said socket to preload said bearing, said loading means including an antifriction bearing engaging the inner end of said sleeve, a tubular member engaging said bearing, a second member mounted upon the shaft coupling element, and a third member in threaded engagement with the last mentioned member and also in engagement with the tubular member, the third member being slit longitudinally and having a tapered and screw threaded longitudinal bore, and a tapered screw member in said bore for spreading the second member into close frictional engagement to iix the adjusted position of said second and third members.

PAUL F. HACKETHAL. ROMUALD KAREY.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,069,846 Pecker Feb. 9, 1937 2,107,785 Grabarse Feb. 8, 1938 2,275,361 Godfrey Mar. 3, 1942 2,396,630 Anderson Mar. 19, 1946 2,425,938 Hoover Aug. 19, i947 2,436,612 Sheets Feb. 24, 1948 

